A virtual machine (VM) is an emulation of a computer system. When executed on appropriate hardware, a VM creates an environment allowing the virtualization of an actual physical computer system (e.g., a server, a mainframe computer, etc.). The actual physical computer system is typically referred to as a “host machine.” Typically, a component on the host machine known as a “hypervisor” (or a “virtual machine monitor”) manages the execution of one or more virtual machines or “guests”, providing a variety of functions such as virtualizing and allocating resources, context switching among virtual machines, etc. The operating system (OS) of the virtual machine is typically referred to as the “guest operating system” or “guest OS.” In some implementations, the guest OS and applications executing within the guest OS can be collectively referred to as the “guest.”
A virtual machine may access a virtual device using guest page addresses corresponding to memory space assigned to the virtual device for purposes of communicating with the virtual device, which is known as memory-mapped input/output (MMIO). The hypervisor may expose a virtual device to the guest to permit the guest to execute instructions on the virtual device. If a virtual device is a virtual peripheral device, such as a virtual printer or virtual video card, the virtual device may be accessed using memory mapped input-output (MMIO).